1. Field of the invention
This invention concerns directional control of permanent magnets, and it is particularly applicable to the simultaneous control of a series of rotors that are rotatable about parallel transversely spaced coplanar axes. Such rotors are suitable for adjusting the attitudes of louvers having horizontal, vertical or inclined axes of rotation in daylight controlling screens.
2. Description of the prior art
Environmental screens have been described in the patent literature having ribbon-like louvers supported only at their ends, each end being attached to a permanent magnet rotor. The angle of the rotors is determined by equilibrium between a control torque produced by a direct magnetic field of adjustable strength and a restoring torque that tends to maintain each rotor at a predetermined angle of repose. The restoring torque is primarily produced by mutual magnetic coupling between adjacent rotors, and it is limited to about .+-.45 degrees rotation because of the double sinusoidal shape of the restoring torque curve. This type of control is therefore not suitable for louvers that require .+-.90 degrees rotation, for example, vertically hanging louvers. Furthermore, the choice of spacing between adjacent rotors is restricted because the magnetic coupling is inversely proportional to the third power of the spacing.